Heavy transformers are supported on transformer pads and one type of pad is disclosed in U.S. Pat. No. 4,023,755 in which the structural support for the load created by the weight of the transformer is provided by a wood and foam core enclosed within a plastic shell. An aperture is formed through the structure and cables from the transformer are lead down into the ground to the source of electricity. There have been instances in the past where a child pushed a piece of wire, similar to a coat hanger, under the transformer and managed to make contact with a high voltage conductor. There have been previous attempts to provide a perimeter barrier around the transformer pad opening and one such device is disclosed in U.S. Pat. No. 4,267,399 and comprises a molded rectangular frame of solid construction which is to be inserted in the transformer opening before the installation of the transformer is completed on the pad. One problem with the solid frame is that it cannot be installed into an existing unit (which is sometimes referred to as "retrofitting") without disconnecting all the cables, and this creates a safety hazard. In addition, the prior frame does not extend below the mounting pad for additional protection. There is a demand for a safety barrier which can be installed after the transformer has been installed on the pad and without disconnecting or removing the cables. There is also a need for a unit which can be disassembled and assembled into any old or new installations. This is particularly important for retrofit.